Surface light source device for recording/reproducing holograms

ABSTRACT

A surface light source device is provided. The surface light source device includes a light source, a beam splitter configured to split a light irradiated from the light source into a plurality of light beams each having a different path, a diffusion unit configured to diffuse the plurality of light beams split by the beam splitter into a surface light, and a collimating unit configured to arrange the plurality of light beams diffused from the diffusion unit in one direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(a) of KoreanPatent Application No. 10-2010-0103684, filed on Oct. 22, 2010, in theKorean Intellectual Property Office, the entire disclosure of which isincorporated herein by reference.

BACKGROUND

1. Field

The following description relates to a surface light source device forrecording and reproducing holograms.

2. Description of the Related Art

Multi-dimensional image display devices, such as 3-dimensional (3D)image display devices, realistically and effectively display 3D imagesand are increasingly used in fields, such as medical imaging, games,advertising, education, military applications, etc. Accordingly,holography methods and stereoscopy methods have been activelyresearched.

In a holography method, overlapping a light incident from an object witha coherent reference light is recorded and reproduced in order to obtaina coherent signal. The holography method is an suitable method forrealizing a multi-dimensional image, such as a 3D image. Since DennisGabor, an English scientist, developed the first hologram in the 1940s,many scientists have conducted research into holography. More recently,a variety of techniques for displaying holograms have been developedincluding, for example, a pulse laser hologram for a dynamic image, astereohologram for a wide spatial view and wide viewing angle, anembossed hologram for mass production, a natural color hologram fordisplaying natural colors, a digital hologram using a digital imagingdevice, and an electronic holography for displaying an electronichologram.

Surface light source devices for recording/reproducing a hologram as a3D image are used in displaying a holographic image. In response to ahologram being optically recorded, a surface light source device thatprovides a coherent surface light is used to form interference fringesof an object beam and a reference beam. Also, a surface light sourcedevice is used for irradiating a surface light as a reproducing light toa medium onto which a hologram is recorded, and the surface light sourcedevice is used to display a 3D image. In addition, in response to ahologram being electrically recorded, a surface light source device isused to reproduce a hologram.

SUMMARY

According to an aspect, a surface light source device is provided. Thesurface light source device including a light source, a beam splitterconfigured to split a light irradiated from the light source into aplurality of light beams each having a different path, a diffusion unitconfigured to diffuse the plurality of light beams split by the beamsplitter into a surface light, and a collimating unit configured toarrange the plurality of light beams diffused from the diffusion unit inone direction.

The diffusion unit may include a plurality of pin holes respectivelycorresponding to the plurality of light beams.

The collimating unit may include a lens array including a plurality ofconvex lens units.

The plurality of convex lens units may be formed to respectivelycorrespond to the plurality of pin holes.

The plurality of convex lens units may have sizes respectivelycorresponding to a cross-section of the plurality of light beamsdiffused while passing through the plurality of pin holes.

The device may further include an optical mask configured to change abeam intensity distribution of a beam collimated by the collimatingunit, at a cross-section of the beam.

The optical mask may have a non-uniform light transmittancedistribution, and the light transmittance distribution may be determinedso that a relatively low light transmittance occurs in an area thatcorresponds to an area where beam intensity is relatively high incomparison to other areas.

The beam splitter may include a plurality of cubic beam splitters.

The beam splitter may include an light splitting member configured tosplit a light irradiated from the light source into a plurality of lightbeams each proceeding in a different direction, and a reflective memberhaving reflective surfaces reflecting the plurality of light beams indirections parallel to each other. The plurality of light beams may berespectively incident on the reflective member at a different incidentangle.

The diffusion unit may include a plurality of pin holes respectivelycorresponding to the plurality of light beams.

The collimating unit may include a lens array including a plurality ofconvex lens units.

The plurality of convex lens units may be formed to respectivelycorrespond to the plurality of pin holes.

The plurality of convex lens units may have sizes respectivelycorresponding to a cross-section of the plurality of light beamsdiffused while passing through the plurality of pin holes.

The light splitting member may include a rotating polygon mirror havinga plurality of mirror surfaces.

The light source may irradiate light so as to scan the mirror surfacesduring a predetermined period along a rotating axis direction of therotating polygon mirror.

The light splitting member may include a galvanometer mirror.

The reflective surface may include a plurality of flat reflectivesurfaces each having a different tilt angle.

The number of the plurality of flat reflective surfaces may correspondto the number of the plurality of light beams split by the lightsplitting member.

A device for recording/reproducing holograms may use the surface lightsource device as a recording light or reproducing light.

In another aspect, a device is provided. The device includes a surfacelight source unit including a beam splitter configured to split a lightirradiated from a light source into a plurality of light beams eachhaving a different path, a diffusion unit configured to diffuse theplurality of light beams split by the beam splitter into a surfacelight, and a collimating unit configured to collimate the diffusedplurality of light beams.

Other features and aspects may be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a surface light sourcedevice;

FIG. 2 is a diagram illustrating a distribution of an optical beam seenfrom a cross-section cut along a line of A-A′ of FIG. 1;

FIG. 3 is a diagram illustrating variations of a light transmission ofan optical mask of FIG. 1 with positions in the optical mask 170;

FIG. 4 is a diagram illustrating a distribution of a light beam seenfrom a cross-section cut along a line of B-B′ of FIG. 1;

FIG. 5 is a diagram illustrating another example of a surface lightsource device;

FIG. 6 is a diagram illustrating a distribution of a light beam seenfrom a cross-section cut along a line of C-C′ of FIG. 5;

FIG. 7 is a diagram illustrating another example of a surface lightsource device;

FIG. 8 is a view illustrating an example of a method of determining tiltangles of flat reflective surfaces in a reflective member used in a beamsplitter of FIG. 7; and

FIG. 9 is a view of the surface light source device of FIG. 7illustrating an arrangement relationship where a plurality of flatreflective surfaces of a reflective member correspond to pin holes and alens array.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. Accordingly, various changes,modifications, and equivalents of the systems, apparatuses and/ormethods described herein will be suggested to those of ordinary skill inthe art. Also, descriptions of well-known functions and constructionsmay be omitted for increased clarity and conciseness.

FIG. 1 illustrates an example of a surface light source device 100, FIG.2 illustrates a distribution of an light beam seen from a cross-sectioncut along a line of A-A′ of FIG. 1; FIG. 3 illustrates variations of alight transmission of an optical mask 170 of FIG. 1 according topositions in the optical mask 170, and FIG. 4 illustrates a distributionof an light beam seen from a cross-section cut along a line of B-B′ ofFIG. 1.

Referring to FIG. 1, the surface light source device 100 includes anlight source 110, a beam splitter 120 for splitting a beam generated bythe light source 110, a diffusion unit 130 for diffusing the split beam,and a collimating unit for arranging the beam diffused from thediffusion unit 130.

A coherent laser light source may be used as the light source 110. Also,the light source 110 may be configured to irradiate a light having awavelength in a blue or an i-line band as a light having a shortwavelength so as to produce an increased resolution when a hologram isrecorded in comparison to a hologram produced with a light having alonger wavelength.

The beam splitter 120 is used to split a light irradiated from the lightsource 110 into plurality of light beams each having a different path.The beam splitter 120 may include, for example, a plurality of cubicbeam splitters. A number of the split light beams corresponds to anumber of the cubic beam splitters, and the plurality of cubic beamsplitters may be disposed in one-dimensional or two-dimensional arrays.

The diffusion unit 130 diffuses light beams so that a surface light isconstituted by the plurality of light beams split in the beam splitter120. In this regard, the diffusion unit 130 may include a plurality ofpin holes h respectively corresponding to the plurality of light beamssplit in the beam splitter 120.

The collimating unit arranges the light beams diffused from thediffusion unit 130 as a surface light in one direction and may include acollimating lens 150 to collimate the light beams.

Also, the surface light source device 100 may also include the opticalmask 170 which changes a beam intensity distribution of a beamcollimated by the collimating lens 150, at a cross section of the beam.In response to the collimated beam intensity distribution of a beam notbeing uniform, the optical mask 170 is used to change the beam intensitydistribution to be uniform. For example, in response to the light beamsbeing diffused from the diffusion unit 130 and constituting a surfacelight, an intensity of beam may be greater in an area where the beamsoverlap than an intensity of beam in an area where the beams do notoverlap. FIG. 2 illustrates a distribution of the light beams. Referringto FIG. 2, an intensity of beams in areas R2 where the beams overlap isgreater than that in areas R1 where the beams do not overlap. Due to thenon-uniform distribution of light intensities of the beams, the opticalmask 170 may have a non-uniform light transmittance distribution so asto offset intensity differences of the beams. As illustrated in FIG. 4,a light transmittance of the optical mask 170 may vary according topositions in the optical mask 170. In consideration of the beamdistribution, a light transmission distribution may be determined insuch a way that a relatively low light transmittance occurs in areasthat correspond to areas where an intensity of beam is relatively highin comparison to other areas. As illustrated in FIG. 3, the optical mask170 includes first areas 171 corresponding to areas R1 where anintensity of beams is relative low and second areas 172 corresponding toareas R2 where an intensity of beams is relatively high. The opticalmask 170 may offset a difference in the intensity of beams of the areasR1 and R2, and a light transmittance of the second areas 172 may belower than the light transmittance of the first areas 171. Thenon-uniform beam distribution illustrated in the cross-section cut alongthe line A-A′ is changed to a uniform beam distribution as illustratedin FIG. 4 due to the optical mask 170 having a light transmittancedistribution that may offset the non-uniform beam distribution.

FIG. 5 illustrates another example of a surface light source device 200and FIG. 6 illustrates a distribution of a light beam seen from across-section cut along a line of C-C′ of FIG. 5. A collimating unit ofthe surface light source device 200 includes a lens array 250 accordingto the current example, which is the difference from the surface lightsource device 100 of the previous example. The lens array 250 includes aplurality of convex lens units. The plurality of convex lens unitsrespectively corresponds to the plurality of pin holes h. The pluralityof convex lens units may have sizes respectively corresponding to across-section of the plurality of light beams diffused while passingthrough the plurality of pin holes h. The lens array 250 may alsoinclude a fine-sized micro-lens array. Accordingly, areas where thediffused beams overlap are reduced in response to the beams beingcollimated in one direction. Accordingly, an uniform beam distributionas shown in FIG. 6 may be obtained even if the optical mask 170 of FIG.1 is not used.

FIG. 7 illustrates another example of a surface light source device 300,FIG. 8 is a view for illustrating an example of a method of determiningeach tilt angle of flat reflective surfaces S₁₁, S₁₂ . . . in areflective member 340 used in a beam splitter of FIG. 7, and FIG. 9 is aview of the surface light source device 300 of FIG. 7 illustrating anarrangement relationship where the plurality of flat reflective surfacesS₁₁, S₁₂ . . . of the reflective member 340 correspond to the pin holesh and the lens array 250.

In the current example, the beam splitter has a folded configuration sothat a space for the entire system may be reduced in comparison to abeam splitter having a non-folded configuration.

Referring to FIG. 7, the surface light source device 300 includes thelight source 110, a beam splitter including a light splitting member 320and the reflective member 340, the diffusion unit 130, and the lensarray 250.

The light splitting member 320 splits light L irradiated from the lightsource 110 into a plurality of light beams L_(1i), L_(2i), and L_(3i)each proceeding into a different direction. The light splitting member320 may be, for example, a rotating polygon mirror including a pluralityof mirror surfaces 320 a. As another example, the light splitting member320 may be a galvanometer mirror. The reflective member 340 includes thereflective surface 342 which reflect the plurality of light beamsL_(1i), L_(2i), and L_(3i). The light beams are respectively incident atdifferent incident angles and split by the light splitting member 320 aslight beams L_(1r), L_(2r), and L_(3r) that are parallel to each other.As illustrated in FIG. 8, the reflective surface 342 may include aplurality of flat reflective surfaces 342 a, 342 b, and 342 c eachhaving a different tilt angle. A number of the plurality of flatreflective surfaces 342 a, 342 b, and 342 c correspond to the pluralityof light beams L_(1i), L_(2i), and L_(3i) split by the light splittingmember 320. The tilt angles are determined in such a way that the lightbeams L_(1i), L_(2i), and L_(3i) reflected by the plurality of flatreflective surfaces 342 a, 342 b, and 342 c are parallel to each other.

As another example, regarding the light L irradiated from the lightsource 110, angles of the light L reaching the mirror surfaces 320 avary according to rotation of the light splitting member 320 and therebythe light L is split into the plurality of light beams L_(1i), L_(2i),and L_(3i) each having a different direction. The light beam L_(1i)incident onto the flat reflective surface 342 a at an incident angle ofθ_(1i) proceeds in a predetermined direction as a light beam L_(1r)reflected with a reflective angle θ_(1r). Due to Snell's reflection law,the reflective angle θ_(1r) is the same as the incident angle of θ_(1i).Similarly, the light beam L_(2i) incident onto the flat reflectivesurface 342 b at an incident angle of θ_(2i) proceeds in a predetermineddirection as a light beam L_(2r) reflected with a reflective angleθ_(2r). The reflective angle θ_(2r) is the same as the incident angle ofθ_(2i). Also, the light beam L_(3i) incident onto the flat reflectivesurface 342 c with an incident angle of θ_(3i) proceeds in apredetermined direction as a light beam L_(3r) reflected with areflective angle θ_(3r). The reflective angle θ3 _(r) is the same as theincident angle of θ_(3i). Tilt angles φ₁, φ₂, and φ₃ of the flatreflective surfaces 342 a, 342 b, and 342 c are determined so that thelight beams L_(1i), L_(2i), and L_(3i) are respectively reflected fromthe flat reflective surfaces 342 a, 342 b, and 342 c in the samedirection. In other words, L_(1r), L_(2r), and L_(3r) are parallel toeach other.

As illustrated in FIG. 9, a plurality of flat reflective surfaces S₁₁,S₁₂, S₁₃, S₂₁, S₂₂, S₂₃, S₃₁, S₃₂, and S₃₃ may be arranged in atwo-dimensional array to correspond to the pin holes h of the diffusionunit 130.

The flat reflective surfaces (S_(nm), n=1, 2, 3, m=1, 2, 3) may beformed so that the plurality of light beams L_(nmi) split from the lightsplitting member 320 may two-dimensionally scan the reflective surface342. For example, light incident onto the mirror surface 320 a isscanned in a direction perpendicular to a rotating axis according to therotation of the light splitting member 320. In response to a directionof light incident from the light source 110 being set to repeatedly scanthe mirror surface 320 a in a predetermined period along a rotating axisdirection, the plurality of light beams L_(nmi) split from the lightsplitting member 320 are respectively directed the flat reflectivesurfaces S_(nm) each arranged in a two-dimensional array.

Directions of basis vectors a_(n)(n=1, 2, 3, . . . ) and b_(m)(m=1, 2, 3. . . ) defining the flat reflective surfaces S_(nm) are determinedaccording to the principle described with reference to FIG. 8. In thedrawings, b₁, b₂, and b₃ have the same direction for conciseness; inanother example, directions of the b₁, b₂, and b₃ may be different fromeach other so that the light beams L_(nmr) are reflected from the flatreflective surfaces S_(nm) in the same direction. Also, based on theteachings herein, the number of the flat reflective surfaces S_(nm) maybe a number other than 9. In response to the number of the flatreflective surfaces S_(nm) increasing, the reflective surface 342 maybecome more shaped like a curve.

The light beams L_(nmr) reflected from the reflective member 340 facethe diffusion unit 130. The diffusion unit 130 includes the plurality ofpin holes h each corresponding to the light beams L_(nmr). The incidentlight beams pass through the pin holes h and are diffused in a surfacelight form. After passing the diffusion unit 130, the incident lightbeams are incident onto the lens array 250. The lens array 250 mayinclude the plurality of convex lens units. The plurality of convex lensunits respectively corresponding to the plurality of pin holes h, andthe plurality of convex lens units may have sizes respectivelycorresponding to a cross-section of the plurality of light beamsdiffused while passing through the plurality of pin holes h. The lensarray 250 may also include fine-sized micro-lens array. Areas withoverlapping beams are reduced when the beams diffused from the diffusionunit 130 are arranged while passing through the lens array 250, and dueto a reduction in overlap, a uniform beam distribution D may beobtained. Also, an optical mask having a non-uniform light transmittancedistribution may be further included according to the exampleillustrated in FIG. 3, in order to make the beam distribution moreuniform. Also, as illustrated in FIG. 1, both the collimating lens 150and the optical mask 170 may be used.

As described above, according to the one or more of the above examples,the surface light source device may change a coherent light into alarge-sized surface light. Also, the surface light source deviceincludes a beam splitting structure, which may have a reduced volume,and thus, the entire system may be simplified. In addition, acollimating structure, which may improve a beam uniformity of surfacelight, is provided so as to provide a surface light having betteruniformity.

Also, the surface light source device described above may be used inrecording light and/or reproducing light in a device forrecording/reproducing 3D holographic images.

The surface light source device may be incorporated into various devicesincluding, for example, a television, a cellular phone, a monitor, atablet computer, a laptop computer etc.

A number of examples have been described above. Nevertheless, it will beunderstood that various modifications may be made. For example, suitableresults may be achieved if the described techniques are performed in adifferent order and/or if components in a described system,architecture, device, or circuit are combined in a different mannerand/or replaced or supplemented by other components or theirequivalents. Accordingly, other implementations are within the scope ofthe following claims.

1. A surface light source device comprising: a light source; a beamsplitter configured to split a light irradiated from the light sourceinto a plurality of light beams each having a different path; adiffusion unit configured to diffuse the plurality of light beams splitby the beam splitter into a surface light; and a collimating unitconfigured to arrange the plurality of light beams diffused from thediffusion unit in one direction.
 2. The device of claim 1, wherein thediffusion unit comprises a plurality of pin holes respectivelycorresponding to the plurality of light beams.
 3. The device of claim 2,wherein the collimating unit comprises a lens array comprising aplurality of convex lens units.
 4. The device of claim 3, wherein theplurality of convex lens units are formed to respectively correspond tothe plurality of pin holes.
 5. The device of claim 4, wherein theplurality of convex lens units have sizes respectively corresponding toa cross-section of the plurality of light beams diffused while passingthrough the plurality of pin holes.
 6. The device of claim 2, furthercomprising an optical mask configured to change a beam intensitydistribution of a beam collimated by the collimating unit, at across-section of the beam.
 7. The device of claim 6, wherein the opticalmask has a non-uniform light transmittance distribution, and the lighttransmittance distribution is determined so that a relatively low lighttransmittance occurs in an area that corresponds to an area where beamintensity is relatively high in comparison to other areas.
 8. The deviceof claim 1, wherein the beam splitter comprises a plurality of cubicbeam splitters.
 9. The device of claim 1, wherein the beam splittercomprises: an light splitting member configured to split a lightirradiated from the light source into a plurality of light beams eachproceeding in a different direction; and a reflective member havingreflective surfaces reflecting the plurality of light beams indirections parallel to each other, wherein the plurality of light beamsare respectively incident on the reflective member at a differentincident angle.
 10. The device of claim 9, wherein the diffusion unitcomprises a plurality of pin holes respectively corresponding to theplurality of light beams.
 11. The device of claim 10, wherein thecollimating unit comprises a lens array comprising a plurality of convexlens units.
 12. The device of claim 11, wherein the plurality of convexlens units are formed to respectively correspond to the plurality of pinholes.
 13. The device of claim 12, wherein the plurality of convex lensunits have sizes respectively corresponding to a cross-section of theplurality of light beams diffused while passing through the plurality ofpin holes.
 14. The device of claim 9, wherein the light splitting membercomprises a rotating polygon mirror having a plurality of mirrorsurfaces.
 15. The device of claim 14, wherein the light sourceirradiates light so as to scan the mirror surfaces during apredetermined period along a rotating axis direction of the rotatingpolygon mirror.
 16. The device of claim 8, wherein the light splittingmember comprises a galvanometer mirror.
 17. The device of claim 13,wherein the reflective surface comprises a plurality of flat reflectivesurfaces each having a different tilt angle.
 18. The device of claim 17,wherein the number of the plurality of flat reflective surfacescorresponds to the number of the plurality of light beams split by thelight splitting member.
 19. A device for recording/reproducing hologramsusing the surface light source device of claim 1 as a recording light orreproducing light.
 20. A device comprising: a surface light source unitcomprising: a beam splitter configured to split a light irradiated froma light source into a plurality of light beams each having a differentpath; a diffusion unit configured to diffuse the plurality of lightbeams split by the beam splitter into a surface light; and a collimatingunit configured to collimate the diffused plurality of light beams.